This invention generally relates to outdoor lighting systems for illuminating highways or airports and the like, and is specifically concerned with an improved system of the type wherein outdoor lights are mounted on a plurality of spaced-apart tubular masts and powered by a common, underground circuit breaker.
Outdoor lighting systems for illuminating streets and highways are known in the prior art. Such lighting systems typically include a plurality of lighting units spaced along the road or highway, each of which includes an electric light that is supported on the distal end of a tubular mast whose proximal end is anchored into the ground. In some instances, the lights are suspended over the street or highway by a cantilevered support member attached to the mast. In other instances, a ring of high intensity lights circumscribes the distal end of the mast. In either instance, an electric power cable connects each of the spaced-apart, mast-supported lights to a common power source in the form of the output of an above-ground circuit breaker. The electric power cable for each lighting unit includes a first portion that is connected to the light source and disposed within the hollow mast, and a second portion disposed underground and connected to a power source in the form of either the aforementioned circuit breaker, or the power cable of an adjacent lighting unit. Additionally, both a fuse assembly and a lightning arrestor are disposed within the hollow end of the mast and connected between the first and second portions of the electric cable for preventing current overloads to the light fixture, and for protecting the circuit breaker from current surges caused by lightning. To provide access to the fuse assembly and lightning arrestor, a removable panel is usually provided at the base of the mast. Additionally, the wrenching tensile forces applied throughout the length of the cable just before the breakage thereof at the fuse assembly splices often weakens splices and other connections made with adjacent lighting units, setting the stage for future maintenance problems that are difficult to diagnose and solve.
While such prior art lighting system are widely used to illuminate streets, highways, and virtually any place where large amounts of outdoor lighting is required, the applicant has observed a number of shortcomings associated with the design of these systems which significantly impairs their overall usefulness.
For example, if one of the masts of such a system should be knocked down as a result of an automobile collision, the stresses applied to the cable within the mast often causes it to break at the connections made with the fuse assembly. As these connections are typically made by way of splices, the tension applied to the cable from the automobile collision tears the splices apart, dangerously exposing wires that are "hot". These exposed, hot wires can in turn conduct dangerous electrical currents through the knocked-down mast (which is typically made of a conductive metal) or even the body of the colliding car. Even if the collision causes the exposed conductors of the broken cable splice to short circuit and trip the circuit breaker, this somewhat safer result is not particularly desirable, as such tripping will cut off the current flowing to all of the other mast-supported lights that are serially connected to the breaker, thus surrounding the area around the broken mast in total darkness if the collision occurs at night. Additionally, the wrenching tensile forces applied throughout the length of the cable just before the breakage thereof at the fuse assembly splices often weakens splices and other connections made with adjacent lighting units, setting the stage for future maintenance problems that are difficult to diagnose and solve.
Still another shortcoming of prior art lighting systems results from the positioning of the fuse assembly and lightning arrestor in the base of the hollow mast in each lighting unit. Because such masts usually have openings at their upper ends or sides for structural reasons, the interior of such masts often becomes the home of wildlife that is either potentially hostile (such as wasps, poisonous snakes, or rats) or of the type apt to build nests around these components (such as birds or squirrels). The presence of such animal life significantly impairs the replacement of fuses of burned-out lightning arrestors by either assaulting the maintenance personnel who carry out such operations, or by creating physical obstructions (such as nests) that must be removed incident to such operations. Additionally, the spliced connection between the lightning arrestor and the cable that supplies electrical power to the light source makes it difficult to replace this component in the event of a burn out of the surge arrestor circuit in the arrestor from a bolt of lightning striking the conductive mast.
A final shortcoming of such prior art systems results from the relatively easy access to the components and cables located inside the masts near the proximal ends thereof. The present access panels are easily opened by vandals who may tamper with or destroy the components inside, or by thieves who attach the cable leading to the circuit breaker to a truck and pull it out of the ground for the purpose of selling the relatively large amounts of copper in it. In recent years, such vandalism and theft has been a major drain on the maintenance budgets for such lighting system in both the public and the private sectors of the economy.
Clearly, there is a need for an improved outdoor lighting system having some sort of means for preventing the creation of dangerous exposed "hot" wires in the event of a collision between an automobile and a mast, as well as a means for preventing dangerous destructive forces generated by such collisions from being transmitted from the power cable inside the mast to other splices and connections all throughout the system. Ideally, such a system should deploy the fuse assembly and lightning arrestor in a location which is reasonably accessible to maintenance personnel, but completely inaccessible to potentially hostile wildlife. Such a system should further make is difficult, if not impossible, for vandals or thieves to destroy or steal large lengths of heavy copper cables or other valuable components located inside the masts. Finally, it would be desirable if such a system could be easily retrofitted onto prior art, mast-type outdoor lighting systems in a relatively quick and cost-efficient manner.